Al Thin Films Research Articles

Preparation and Study of Properties of CdO: Al Thin Films Prepared by Chemical Spraying

Preparation and Study of Properties of CdO: Al Thin Films Prepared by Chemical Spraying

Improvement of the Electromigration Resistance of Al Thin-Film Interconnection by Controlling the Crystallinity of Grain Boundaries

The degradation process of the crystallinity of grain boundaries in Al thin-film interconnections was visualized by applying EBSD analysis under high current density. The grain boundary diffusion was accelerated by electromigration only along random grain boundaries with low crystallinity. The crystallinity (IQ value obtained from EBSD analysis) of grain boundaries varied drastically as strong functions of manufacturing process such as deposition method, temperature of thin-film deposition, gas pressure during the deposition, substrate material, and so on. The effective activation energy of self-diffusion of component element along random grain boundaries was found to be dominated by the crystallinity of random grain boundaries. The measured activation energy obtained from the low-crystallinity interconnections was much lower than that obtained from the thermodynamically stable bulk material, and therefore, the diffusion constant due to electromigration was drastically increased, resulting in the drastic decrease of the lifetime of the interconnections. The lifetime of the interconnections was, therefore, improved by increasing the crystallinity of grain boundaries.

Resistive switching characteristics of sol-gel derived La2Zr2O7 thin film for RRAM applications

Amorphous La2Zr2O7 thin films were fabricated using the sol-gel method and the bipolar resistive switching behavior of the metal(Al or Ti)/LZO/ITO devices were systematically investigated. The effect of film thickness, top electrodes, and post-annealing treatment conditions on the RS characteristics of the La2Zr2O7 thin films were also discussed. The film thickness increases significantly as the number of spin-coating layers increases, leading to a higher operation voltage and fewer switching cycle times. In addition, the RS properties of the devices are affected by the work function difference between the top and the bottom electrodes. All devices exhibited similar conduction mechanisms, which are described by the ohmic conduction in the low resistance state and space-charge limited current in the high resistance state. Moreover, the RS performance can be profoundly improved by the post-annealing treatment because of the formation of a thicker AlOx interface layer between the Al and LZO thin films, which was revealed via TEM images. The optimized RRAM performances are 1971 cycle times and high stable retention time for over 105 with a Ron/Roff ratio of around 101 at a post-annealing temperature of 300°C. The multilevel RS performances are also observed. Besides, this device maintained a large enough memory window in the retention test at 85°C thermal stress. The longer life is to be expected.

Influences of aluminum doping on the microstructures and electrical properties of tantalum nitride thin films before and after annealing

Ta–N–Al thin films were produced by reactive sputtering with two different TaAl alloys (Al 10 at.% and 20 at.%) for use as resistive materials for thin film chip resistors. Changing the N2 gas flow of the N2/Ar plasma and the Al ratio in TaAl alloy resulted in different microstructures and electrical properties of the Ta–N–Al thin film. The resistivity of the thin film sputtered by TaAl (Al 20 at.%) alloy was 1.23 times that sputtered by Ta under 20% N2/Ar. After deposition, rapid thermal processing was applied to anneal the thin films for 5 min at 600 °C, 650 °C, and 700 °C under N2 (99.995%) atmosphere, causing the Ta2N and TaN crystalline phase formation. Al in Ta–N–Al was observed to hinder Ta2N and TaN crystalline phase formation during annealing. It is crucial to dope Al ith Ta–N appropriately to obtain a near-zero temperature coefficient of resistance (TCR) after annealing. The TCR of Ta–N–Al thin film, sputtered by TaAl (Al 20 at.%) alloy, was substantially affected by the annealing temperature. However, the thin film sputtered by TaAl (Al 10 at.%) alloy under 16% N2/Ar can achieve a TCR of −1.8 ppm/°C and 1.4 ppm/°C after annealing at 600 °C and 650 °C, respectively.

Influence of synthesis parameters and thermal annealing on grain size of polycrystalline aluminum thin film

The thin polycrystalline aluminium films were synthesized on monocrystalline silicon substrates by ion-plasma sputtering. The synthesis was carried out at temperatures of 80 and 160°C and deposition rate of 10 and 110 nm/min. As-deposited films were annealed for 15 h at 550°C. The morphology of aluminium films before and after annealing was obtained using SEM images. The surfaces of as-deposited Al thin films, synthesized at high temperature, were uneven, while for low temperature films they were smooth enough with Al hillocks on the top of the film. After thermal annealing, morphology of the films was changed slightly. XRD patterns were obtained to calculate the average Al grain size of as-deposited and annealed films. The XRD analysis showed that an increase in the synthesis temperature leads to an increase in the average grain size from 50 to 84 nm and that increase in the rate of Al film synthesis leads to an increase in the average grain size from 50 to 63 nm. As the result of annealing, the average grain size increased for all samples and the final meaning was from 78 to 140 nm.

Influence of Impurities on the Front Velocity of Sputter Deposited Al/CuO Thermite Multilayers.

CuO and Al thin films were successively deposited using direct current (reactive) magnetron sputter deposition. A multilayer of five bilayers was deposited on glass, which can be ignited by heating a Ti resistive thin film. The velocity of the reaction front which propagates along the multilayer was optically determined using a high-speed camera. During the deposition of the aluminum layers, air was intentionally leaked into the vacuum chamber to introduce impurities in the film. Depositions at different impurity/metal flux ratios were performed. The front velocity reaches a value of approximately 20 m/s at low flux ratios but drops to approximately 7 m/s at flux ratios between 0.6 and 1. The drop is rather abrupt as the front velocity stays constant above flux ratios larger than 1. This behavior is explained based on the hindrance of the oxygen transport from the oxidizer (CuO) to the fuel (Al).

Synthesis and characterization of TiO2: Al thin films for bacteria resistance in the implanted dental

Synthesis and characterization of TiO2: Al thin films for bacteria resistance in the implanted dental

Comparison of characteristic properties of Al, Ga, and In-doped ZnO thin films formed by sol-gel method

Herein, we examine the effect of doping with Indium (In), Gallium (Ga), and Aluminum (Al) (group III elements) on the structural, optical, and vibrational properties of ZnO thin films . The characteristic properties of the ZnO films prepared by the sol-gel dip-coating method are explored by utilizing X-ray diffraction, optical spectroscopy , and Raman scattering measurements. XRD analyzes exhibit that the crystallite size reduces upon doping by Ga and Al, while it increases with In, and all films have hexagonal wurtzite structure. Additionally, Raman measurements indicate that the dominant two peaks at around 104 and 445 cm −1 are related to E 2 low and E 2 high phonon modes of ZnO, respectively. The low-frequency mode ( E 2 low ) is affected by dopant atoms, whereas the high-frequency mode ( E 2 high ) of the wurtzite phase is not influenced by the dopant. Moreover, E dop-atom phonon mode appears at low frequencies and the intensity ratio, I( E dop.atom )/I( E 2 low ), decreases as the ionic radius of dopant atoms increases. UV–Vis spectra reveal that the film transparency, optical band gap, Urbach energy, and refraction index can be effectively tuned by dopant atoms. • Al, Ga and In-doped ZnO films are prepared by sol-gel dip coating method. • XRD and Raman spectra show that films have hexagonal wurtzite structure. • The intensity of E 2 low mode rises as the ionic radius of the dopant atom increases. • The optical band gap of In-doped ZnO reduces due to expansion of crystallite size. • Raman and XRD measurements reveal that the films are under compressive stress.

Tensile Deformation of Al Thin Films Studied by In-situ TEM and Molecular Dynamics Simulations

Tensile Deformation of Al Thin Films Studied by <i>In-situ</i> TEM and Molecular Dynamics Simulations

TiO2 thin films derived by facile sol-gel method: Influence of spin rate and Al-doping on the optical and electronic properties

Titanium dioxide (TiO2) thin films with enhanced properties have been synthesized by sol-gel method and they can be used for various applications as in field-effect transistors (FETs), sensors, photovoltaics etc. The properties of TiO2 thin films were optimized by changing spin speed (1000 and 3000 rpm) and doping Al in the TiO2 lattice. The influence of spin speed and Al doping on the grain orientation and surface morphology of titania were studied using x-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy (TEM). Uniform, smooth and compact TiO2 thin films having tetragonal anatase phase and a band gap of 3.54 eV along with an optimum thickness and high dielectric constant of ~28 were obtained at a spin speed of 3000 rpm. These films have been previously reported as a gate dielectric layer in the fabrication of flexible ZnO:Al thin film transistor with a mobility of 4.96 cm2/Vs, therefore, the samples prepared at different spin speed could be useful for the fabrication of organic and inorganic FETs. Detailed study was performed on Al-doped TiO2 thin films. XRD and various vibrational modes noticed in the Raman spectra confirmed the formation of crystalline TiO2 films with a pure anatase tetragonal phase. A systematic shift in (101) plane in XRD and E1 g mode in Raman spectra confirms the substitutional doping of Al in the TiO2 matrix. A red shift in the band gap energy with increased transmittance in visible region was observed for the Al-doped TiO2 samples. The higher value of Urbach energy for the Al-doped samples reveals the presence of defects related to oxygen which were further studied by the photoluminescence spectra (PL). AFM images revealed compact, void free and uniform deposition of both TiO2 and TiO2: Al films. The particle size was found to be in the range of 30–40 nm and 40–100 nm for TiO2 and TiO2: Al, respectively. Enhanced electrical conductivity was observed for the Al-doped TiO2 thin films. The current Al-doped TiO2 system with enhanced optical, morphological and electrical properties could be a potential candidate in optoelectronic, sensing and photovoltaics applications.

Location-Optoelectronic Property Correlation in ZnO:Al Thin Film by RF Magnetron Sputtering and Its Photovoltaic Application.

In this study, a radio-frequency magnetron sputter system was used to deposit Al2O3 doped ZnO (AZO) thin films at room temperature, and the soda lime glass (SLG) substrates were placed at different zones relative to the center of the sample holder under the target. The samples were then analyzed using an X-ray diffractometer, Hall-effect measurement system, UV-visible spectrophotometer, and X-ray photoelectron spectroscopy. It was found that the electrical, structural, and optical properties of AZO films strongly depend on the target racetrack. The AZO thin film grown at a location outside the racetrack not only has the most suitable figure of merit for transparent conductive films, but also retains the least residual stress, which makes it the most suitable candidate for use as a CZTSe transparent conductive layer. When applied to CZTSe solar cells, the photoelectric efficiency is 3.56%.

Origin of operating voltage increase in deep UV light-emitting diodes with ITO/Al reflector

In an attempt to further elucidate the operating voltage increase in a vertical UV-C LED with p-electrode composed of transparent conducting Sn-doped indium oxide (ITO)/Al reflector, the interface formation between ITO and Al thin film was studied by using scanning transmission electron microscopy in combination with electron energy loss spectroscopy. It was confirmed that the oxidized layer was formed at the interface of the ITO/Al electrode in accordance with the thermal annealing. It was found that not only the thickness of oxide formation grew with the increased annealing temperature, the content of oxygen also increased. Moreover, it was also ascertained that the prolonged annealing time at high temperature induced the indium diffusion into the Al-oxide layer.

Single germanene phase formed by segregation through Al(111) thin films on Ge(111)

We have obtained single phase monolayer germanene on aluminum (111) thin films grown on a germanium (111) template by atomic segregation epitaxy, a preparation method differing from molecular beam epitaxy used in previous works. This 2 × 2 reconstructed germanene phase matching an Al(111)3 × 3 supercell has been prepared in large areas upon annealing at 430 °C. Detailed studies have been carried out using scanning tunneling microscopy (STM), low-energy electron diffraction, Auger electron spectroscopy, and synchrotron radiation photoemission spectroscopy. First-principles calculations based on the density function theory along with atomic-scale STM images reveal the atomic structure with one protruding Ge atom per 2 × 2 germanene supercell and a characteristic dispersing band originating from the germanene sheet slightly coupled to the first layer Al atoms underneath. Instead, upon annealing at lower temperatures, multi-phase regions comprise twisted germanene domains in correspondence with an Al(111)√7×√7 R ± 19.1° superstructure as obtained in previous studies.

Growth temperature on ZnO:Al thin films morphology and optical properties

ABSTRACT ZnO:Al thin films were deposited on a glass substrate by a sol–gel method with a combined two-step, spin coating and growth treatment in a water bath. The effect of Al incorporation and the bath growth temperature on the crystal structure, morphology and optical properties of the samples are investigated. The results showed that the morphology of 3% Al-doped film was rod-like nanostructure at 40°С and granular at 60 and 90°С. The lattice strain increases after the Al-doping at 40 and 60°C. And the strain of 3% Al-doped film decreased with increasing the bath growth temperature. The optical band gap of pure and 3% Al-doped film at different bath growth temperature is calculated. Relatively better visible light transmittance and photoluminescence (PL) characteristics were obtained at 40°С. Blue emission associated with surface defects was observed.

Magnetron sputtering technique for analyzing the influence of RF sputtering power on microstructural surface morphology of aluminum thin films deposited on SiO2/Si substrates

In this research, aluminum (Al) thin films were deposited on SiO2/Si substrates using RF magnetron sputtering technique for analyzing the influence of RF sputtering power on microstructural surface morphologies. Different sputtering RF powers (100–400 W) were employed to form Al thin films. The characteristics of deposited Al thin films are investigated using X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier-transforms infrared (FTIR) spectroscopy. The X-ray diffraction (XRD) results demonstrate that the deposited films in low sputtering power have amorphous nature. By increasing the sputtering power, crystallization is observed. AFM analysis results show that the RF power of 300 W is the optimum sputtering power to grow the smoothest Al thin films. FTIR results show that the varying RF power affect the chemical structure of the deposited films. The SEM results show that by increasing the sputtering power leads to the formation of isolated texture on the surface of substrate. In conclusion, RF power has a significant impact on the properties of deposited films, particularly crystallization and shape.

Hydrogenation of Boron Carbon Nitride Thin Films for Low-k Dielectric Applications

The influence of hydrogenation on boron carbon nitride (BCN) thin films was investigated for low-k dielectric applications. The BCN thin films were deposited using radio-frequency magnetron sputtering in hydrogen, nitrogen, and argon ambiance. The hydrogen/nitrogen reactive gas flow was varied from 0/10 to 10/10 to achieve a varying range of hydrogen doping. Elemental composition and chemical bonding studies of the films were analyzed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). XPS results confirmed the formation of B-C-N atomic hybridization, and FTIR confirmed the hydrogen doping by evidence of C–H bonds. Metal insulator metal structures were fabricated using Al and BCN thin films to measure electrical properties such as dielectric constant and resistivity. Hydrogenation of BCN caused a 68% decrease in the k value from 6.2 to 2 due to the formation of non-polar bonds. The k value of 2 reported in this study is the lowest value achieved for hydrogenated BCN films deposited by the RF magnetron sputtering technique.

Rapid growth of ultra-long Al whiskers from TiN/Al/Si island structures

This paper aims to fabricate longer Al whiskers with shorter heating time by using stress-induced migration. The island structure sample, which consists of a rectangular Al thin film on a Si wafer covered with a TiN layer, is heated for rapid growth of Al whiskers. Unique, compressive stress distribution in the Al thin film from the center to the edge of islands during the heating contributes to whisker growth. Si diffusion into the Al thin film during heating promotes atomic diffusion. In order to obtain longer whiskers, a lower heating temperature of 300 °C was found to be better than 500 °C. As a result, a longer Al whisker of approximately 0.5 mm was obtained for 3 h heating time.

PDMS-ZnO Piezoelectric Nanocomposites for Pressure Sensors.

The addition of piezoelectric zinc oxide (ZnO) fillers into a flexible polymer matrix has emerged as potential piezocomposite materials that can be used for applications such as energy harvesters and pressure sensors. A simple approach for the fabrication of PDMS-ZnO piezoelectric nanocomposites based on two ZnO fillers: nanoparticles (NP) and nanoflowers (NF) is presented in this paper. The effect of the ZnO fillers’ geometry and size on the thermal, mechanical and piezoelectric properties is discussed. The sensors were fabricated in a sandwich-like structure using aluminium (Al) thin films as top and bottom electrodes. Piezocomposites at a concentration of 10% w/w showed good flexibility, generating a piezoelectric response under compression force. The NF piezocomposites showed the highest piezoelectric response compared to the NP piezocomposites due to their geometric connectivity. The piezoelectric compound NF generated 4.2 V while the NP generated 1.86 V under around 36 kPa pressure. The data also show that the generated voltage increases with increasing applied force regardless of the type of filler.

Ca-Doped ZnO:Al Thin Films: Synthesis and Characterization

We unveiled the effect of doping on the morpho-structural and opto/electrical properties of Ca-doped ZnO:Al thin films obtained by RF magnetron sputtering. Scanning electron microscopy (SEM) was performed to reveal the surface morphology, while the composition and crystal structure were investigated by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The correlation between the microstructure and the electrical conductivity identifies an increase in electrical conductivity up to 145 × 10−3 Ω−1·m−1 at 5 wt.% Ca doping level with the decrease in the grain size. Furthermore, the presence of Ca dopant triggers the occurrence of the emission peak at 430 nm and an increase of the green emission peak in PL spectra. Corroborating the electrical measurements with X-ray diffraction and optical measurements, one can infer that the electrical conductivity is dominated by intrinsic defects developed during deposition and by the existence of dopants.

Effect of Post-Heating Temperature on Efficiency of Dye-Sensitized Solar Cell with ZnO:Al Thin Films Prepared by Sol-Gel Spin Coating

Dye-sensitized solar cell (DSSC) has a great potential to convert solar light into electricity. In this article, a prototype of DSSC had been successfully fabricated using ZnO:Al thin film and dye from red dragon fruit as a working electrode. ZnO:Al thin films were prepared by a sol-gel spin coating method with variation of post-heating temperatures. The XRD result confirms that all ZnO:Al thin films have a hexagonal structure with crystal sizes of 16 nm to 41 nm. SEM analysis showed the nanoparticles with particle size of 30 nm to 80 nm. The bandgap ranges from 3.16 eV to 3.40 eV. The EIS analysis reveals that charge transfer resistance greatly decreases with the rise of temperature. The efficiency of DSSC gradually improved with increasing the post-heating temperature. ZnO:Al with a post-heating temperature of 600°C had the highest efficiency of 0.398%.